Methylene blue "avatar" brain

Green Discoloration of Human Postmortem Brains: Etiologies and Mechanisms of Discoloration

ABSTRACT

A variety of gross discolorations of human postmortem brains is occasionally encountered and can have diagnostic implications. We describe 3 cases of green discoloration of the human brain observed on postmortem examination. Two patients who succumbed shortly after administration of methylene blue (MB) showed diffuse green discoloration that was detectable as early as 24 hours and was seen for at least 48 hours after MB administration. Green discoloration was largely in cortical and deep gray matter structures with relative sparing of the white matter. In contrast, a patient with severe hyperbilirubinemia who died after intracerebral hemorrhage showed localized bright green bile stained brain parenchyma in the areas surrounding the hemorrhage. We highlight the distinct patterns of discoloration in different causes of green brain discoloration, including MB, bile staining, and hydrogen sulfide poisoning. Recognition of these patterns by practicing pathologists can be used to differentiate between these etiologies and allow correct interpretation in both the medical and forensic autopsy settings.

Greenish-blue discoloration of the brain and heart after treatment with methylene blue

Greenish-blue discoloration of the brain and heart was observed during the autopsy of a 63-year-old woman who had been treated with methylene blue for septic shock following a traffic accident. This "pistachio" or "avatar" discoloration occurs when the colorless metabolite leucomethylene blue is oxidized to methylene blue upon exposure to atmospheric oxygen. Other clinically documented adverse effects of methylene blue include greenish-blue urine and bluish discoloration of the skin and mucosa. In medicine, methylene blue is an inhibitor of nitric oxide synthase and guanylate cyclase with different clinical applications, namely, rapid reversal of circulatory shock that is refractory to fluid administration, inotropic agents, and vasoconstrictors. Postmortem differential diagnosis with putrefaction and hydrogen sulfide poisoning should be made, and forensic pathologists should be aware of methylene blue-related greenish-blue discoloration to avoid unnecessary workup and investigations.